This invention relates to addition polymer compositions derived from free radical polymerizable olefinic monomers, and more particularly to addition polymers containing reactive functionalities. It further relates to addition polymer-rubber copolymer compositions prepared from an addition polymer containing reactive functionalities and a functionalized elastomer reactive therewith, and to a process of preparing the copolymer composition. More specifically, it relates to acrylonitrile-EPDM-styrene, AES, copolymer blends.
Commercial methods for toughening brittle thermoplastics usually involve blending into the plastic an elastomer having a low glass transition temperature. Often, however, the immiscibility and incompatibility of the elastomer with the thermoplastic produce poor physical properties in the blend. A combatibilization strategy is then required to improve physical properties. One strategy involves incorporating a copolymer prepared from the thermoplastic and the elastomer in the blend. The copolymer serves to improve rubber phase dispersion and adhesion, and thereby improves compatibility and physical properties.
Graft copolymers derived from addition polymers and elastomers have traditionally been prepared by polymerizing an olefinic monomer in the presence of a rubber substrate and a free radical initiator. The graft reaction can be accomplished in emulsion, suspension, solution or bulk processes. While such processes are widely used, they disadvantageously require handling and disposing of monomers, solvent, and reaction by-products. Alternatively, addition polymer-rubber copolymers can be formed by melt processing a functionalized addition polymer with a reactive functionalized elastomer. Amines, for example, are known to react with a variety of electrophilic moieties, such as anhydrides, epoxides, and alkyl halides. However, amine-functionalized addition polymers are not readily available for copolymer formation.
It is well known that the free radical polymerization of olefinic monomers containing amine functionalities is fraught with problems. Amine oxidation, free radical trapping, and chain transfer are so extensive that polymerization typically is never realized. Attempts have been made to polymerize the hydrohalide salts of amine-functionalized vinyl monomers, but the variety of organic solvents in which these materials are soluble is limited. As a further disadvantage, amines react with esters, thereby prohibiting the copolymerization of amine-functionalized vinyl monomers with acrylate comonomers. Methods which circumvent some of the aforementioned problems have been developed to produce amine-functionalized addition polymers. For example, U.S. Pat. No. 5,124,410 discloses graft polymers derived from addition polymers of olefinically unsaturated monomers containing protected amine moieties. The protected moieties are disclosed to be capable of conversion at high temperature to free amino groups, which in turn are capable of undergoing reaction with reactive groups on other polymers, thereby leading to copolymer formation. In particular, the graft polymers are taught to comprise a base polymer chain consisting essentially of structural units derived from an olefinically unsaturated hydrocarbon with grafted moieties thereon derived, for example, from t-butyl allylcarbamate. They are further taught to undergo thermal degradation at high temperatures with the elimination of olefin and carbon dioxide, to yield amino-substituted polymers. The latter are capable of reaction with other polymers containing reactive functionalities, to form copolymers.
There are some disadvantages to the graft polymers disclosed in U.S. Pat. No. 5,124,410, and to the process of preparing these graft polymers. Specifically, the concentration of grafted moieties is limited to levels not greater than about 3 weight percent. Moreover, during the process of preparing the graft polymer, the amine protected vinyl comonomer may homopolymerize; for example, to form oligomeric species. Alternatively, there may be unreacted monomer present in the graft polymer.
In view of the above, it remains a desirable goal to prepare an addition polymer from a free radical polymerizable olefinic monomer containing protected amine functionalities. It would be further desirable to control the concentration of protected amine moieties. It would also be desirable if the monomers were soluble in a variety of organic solvents. It would be even more desirable to eliminate problems associated with unreacted monomer in the polymer and homopolymerization of the monomer. To be truly useful, it is necessary for the addition polymer to be cost effective in terms of materials and preparation. If an addition polymer could be prepared containing amine or protected amine moieties, then that polymer might be exploited most advantageously to produce addition polymer-rubber copolymers useful as compatibilizers and useful for improving the physical properties of plastic blends.